Arrangement for the web threading of a multi-roll calender

ABSTRACT

In a paper/board or finishing/converting machine, a calender ( 1 ) comprises a number of rolls ( 2, 3 ) formed into a roll stack, and a number of lift-out rolls ( 4 ), which are arranged in such a way that the web (W) being treated travels from one calender ( 1 ) nip (N) to another via a lift-out roll ( 4 ). Between the calender ( 1 ) roll ( 2, 3 ) and the lift-out roll ( 4 ), the web (W) being treated is supported by means of at least one closing member ( 5, 5′, 6 ) not extending through the nip (N), which closing member is formed by a belt, wire or metal wire ( 7 ), which is arranged to travel via two or more guide rolls ( 4, 8 ).

CROSS REFERENCES TO RELATED APPLICATIONS

This application is a U.S. national stage application of InternationalApplication No. PCT/FI01/00585, filed Jun. 20, 2001, and claims priorityon Finnish Application No. 20001965 filed Sep. 6, 2000, the disclosuresof both of which applications are incorporated by reference herein.

STATEMENT AS TO RIGHTS TO INVENTIONS MADE UNDER FEDERALLY SPONSOREDRESEARCH AND DEVELOPMENT

Not applicable.

BACKGROUND OF THE INVENTION

The invention relates to an arrangement for the web threading of amulti-roll calender of a paper/board or finishing/converting machine,which calender comprises a number of rolls formed into a roll stack, anda number of lift-out rolls, which are arranged in such a way that theweb being treated travels from one calender nip to another via alift-out roll.

With paper machines, the trend has for long been to close open transfersin order to improve runnability. As a result of online calendering, thefirst open transfers are between the dryer section of the paper machineand the calender, and in the set of rolls of the calender.

Nowadays it is known that many web breaks take place precisely at thecalender. These can be eliminated quite efficiently by closing the webthreadings inside the calender and between the dryer section and thecalender. Closing the web threading before and after the calender is notin any way extraordinary. The problem is instead how to accomplishfunctional closing of the web threading in the set of calender rolls.

The web threadings of the calender will in future have to be closed dueto, among other things, higher running speeds, whereby the loads on theweb will increase due to the optimisation of draws, or in general toimprove time efficiency.

One solution for closing the web threading of a calender is disclosed inthe publication U.S. Pat. No. 4,552,620. In it, the belt used forclosing the web threading is looped through the calender nips (seeappended FIG. 1). The paper web travels through each nip between thebelt and the roll. The web is not supported in a completely satisfactorymanner when it travels through the calender. The situation can besomewhat improved by applying the known solution to a calender of theabove-mentioned type which is equipped with lift-out rolls.

SUMMARY OF THE INVENTION

The object of the invention is to provide a reliable arrangement forclosing the web threading of a multi-roll calender.

The solution relating to the invention is characterised in that betweenthe calender roll and the lift-out roll, the web being treated issupported by means of at least one closing member not extending throughthe nip, which closing member is formed by a belt, wire or metal wire,which is arranged to travel via two or more guide rolls.

In one embodiment of the invention this has been implemented in such away that a first closing member picks the web up from the surface of thecalender roll, and a second closing member transfers the web onto thesurface of the next calender roll.

In another embodiment of the invention this has been implemented in sucha way that the closing member picks the web up from the surface of acalender roll and returns the web onto the surface of the same calenderroll, from where the web is conveyed to the next nip along the surfaceof the calender roll. In such a case, the most preferable arrangement issuch that the closing member comprises at least three guide rollslocated at the vertexes of a polygon, and in addition at least one guideroll formed into a lift-out roll and arranged inside the area limited bythe vertexes of the said polygon.

The invention is described in greater detail in the following, withreference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows diagrammatically a calender in which is used closed webthreading according to the prior art.

FIG. 2 shows diagrammatically a multi-roll calender in which is usedclosed web threading according to a first embodiment of the invention.

FIG. 3 shows diagrammatically a multi-roll calender in which is usedclosed web threading according to a second embodiment of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIGS. 2 and 3 show an arrangement according to the invention for closingthe web threading of the multi-roll calender 1 of a paper/board orfinishing/converting machine. The calender 1 comprises a number of rolls2, 3 formed into a roll stack, and a number of lift-out rolls 4, whichare arranged in such a way that the web W being treated travels from onecalender 1 nip N to another via a lift-out roll 4.

FIG. 1 shows a prior art solution which was already referred to in theintroduction to the specification.

In the solution according to FIGS. 2 and 3, the calender 1 comprisesalternately a hard metal roll 3 and a soft fibre or polymer roll 2. Thedrive may take place, for example, by means of one roll, whereby powertransmission to the other rolls takes place by means of frictionalforces, or each roll has its own drive. Since the properties of paperdevelop better on the hard roll side of the nip, a so-called turningnip, which has two soft rolls 2 positioned in succession, is used nearthe centre of the calender. In this way, also the other side of thepaper is treated against the hard rolls 3 at the end part of thecalender.

Between the calender 1 roll 2, 3 and the lift-out roll 4, the web Wbeing treated is supported by means of at least one closing member 5, 5′(FIG. 2), 6 (FIG. 3) not extending through the nip N. The closing memberis formed by a belt, wire or metal wire 7, which is arranged to travelvia two or more guide rolls 4, 8. The closing member 5, 5′, 6 forms itsown endless cycle.

In the embodiment according to FIG. 2, the first closing member 5 picksthe web W up from the surface of the calender 1 roll 2 or 3, and thesecond closing member 5′ transfers the web onto the surface of the nextcalender roll. The grip on the web W is turned between the first andsecond closing members 5, 5′. The guide roll of the closing member 5′marked by reference numeral 4 forms a lift-out roll. The closing member5, 5′ does not pass through the nip N, but the web W is picked up fromeither a polymer roll 2 or a metal roll 3 onto an underpressurized,full-width wire or corresponding closing member 7. Supported by thewire, the web W undergoes the turn of the grip and is transferred ontothe surface of the next roll by means of another underpressurizedtransfer system. The transfer of the web W is ensured by means of anadhesion difference or an overpressure zone. On the other hand, webtension will effect this transfer automatically. The web W is conveyedto the next nip N along the surface of the roll. Between the first andsecond suction transfer systems can be used underpressures of differentmagnitudes, which ensures the changeover of the grip from one system tothe other.

The drives of the calender rolls operate the closing member, or themembers have their own drives. If power is transmitted from the roll tothe wire closing system, this contact may have a positive effect in thatit heats the web.

The amount of evaporation of the calender can be limited by means of theclosing member and air conditioning.

The closing member makes threading possible without having any separatedevices in the stack. Gradually progressing threading also becomespossible. In addition, threading may be of full width.

In the solution relating to FIG. 3, the closing member 6 picks the web Wup from the surface of the calender 1 roll 2 or 3, and returns the web Wonto the surface of the same roll, from where the web is conveyed to thenext nip N along the surface of the calender roll.

In this solution, the closing member 6 comprises at least three guiderolls 8 located at the vertexes of a polygon, and in addition at leastone guide roll 4 formed into a lift-out roll and arranged inside thearea limited by the vertexes of the said polygon.

In the solutions relating to FIGS. 2 and 3, the web W is conveyed to thenip N along the surface of the calender 1 roll 2, 3. At least one guideroll 8 of the closing member 5, 5′, 6 presses the closing means 7 of theclosing member against the calender 1 roll 2, 3.

The closing member 5, 5′, 6 is arranged to be underpressurized to ensurethe transfer.

1. An arrangement for the web threading of a multi-roll calender of apaper/board or finishing/converting machine, which calender comprises aplurality of rolls formed into a roll stack to define a plurality ofcalender nips, and a plurality of lift-out rolls, which are arranged insuch a way that the web being treated travels from one calender nip toanother via a lift-out roll, wherein a first nip is defined between afirst calender roll and a second calender roll, and a first lift-outroll is positioned spaced from the both the first calender roll and thesecond calender roll, wherein as the web travels between the firstcalender roll and the first lift-out roll, the web being treated issupported by at least one closing member not extending through the nip,which closing member is formed by a belt, wire or metal wire, which isarranged to travel via at least two guide rolls.
 2. The arrangement ofclaim 1 wherein the closing member picks the web up from the surface ofa calender roll and returns the web onto the surface of the same roll,from where the web is conveyed to the next nip along the surface of thecalender roll.
 3. The arrangement of claim 2 wherein the closing membercomprises at least three guide rolls located at the vertexes of apolygon, and in addition at least one guide roll formed into a lift-outroll and arranged inside the area limited by the vertexes of the saidpolygon.
 4. The arrangement of claim 1 wherein the web is conveyed tothe nip along the surface of the calender roll.
 5. The arrangement ofclaim 1 wherein at least one guide roll of the closing member pressessaid belt, wire or metal wire of the closing member against the calenderroll.
 6. The arrangement of claim 1 wherein the closing member isarranged to be underpressurized.
 7. An arrangement for the web threadingof a multi-roll calender of a paper/board or finishing/convertingmachine, which calender comprises a plurality of rolls formed into aroll stack to define a plurality of calender nips, and a plurality oflift-out rolls, which are arranged in such a way that the web beingtreated travels from one calender nip to another via a lift-out roll,wherein between the calender roll and the lift-out roll, the web beingtreated is supported by at least one closing member not extendingthrough the nip, which closing member is formed by a belt, wire or metalwire, which is arranged to travel via at least two guide rolls, whereina nip is defined between a first calender roll and a second calenderroll, and wherein a first closing member picks the web up from thesurface of the first calender roll, and a second closing membertransfers the web onto the surface of the second calender roll.
 8. Thearrangement of claim 7 wherein the first closing member picks the web upby engaging a first side of the web, and the second closing memberengages a second, opposite, side of the web.
 9. The arrangement of claim7 wherein at least one guide roll of the first closing member is alift-out roll.
 10. A calender in a paper machine, for the treatment of aweb traveling therethrough, the calender comprising: a plurality ofcalender rolls in a roll stack defining a plurality of nips, the rollstack having a first calender roll which defines a first nip with asubsequent second calender roll, and a third calender roll which definesa second nip with the second calender roll; a plurality of lift-outrolls, wherein a first lift-out roll is spaced from the second calenderroll and the third calender roll and positioned such that the webtravels over the first lift-out roll as it extends between the first nipand the second nip; and a first closing member extending between thesecond calender roll and the first lift-out roll, the closing membersupporting the web as it travels from the first nip to the second nip,the closing member not extending through the first nip or the secondnip, the closing member being a belt, wire, or metal wire which travelsover the first lift-out roll and at least one additional guide roll. 11.The calender of claim 10 wherein the first closing member picks the webup from the surface of the second calender roll and returns the web ontothe surface of the same calender roll, from where the web is conveyed tothe second nip along the surface of tho second calender roll.
 12. Thecalender of claim 11 wherein the closing member travels over at leastthree guide rolls located at the vertexes of a polygon, wherein thefirst lift-out roll is arranged inside the area limited by the vertexesof the said polygon.
 13. A calender in a paper machine, for thetreatment of a web traveling therethrough, the calender comprising: aplurality of calender rolls in a roll stack defining a plurality ofnips, the roll stack having a first calender roll which defines a firstnip with a subsequent second calender roll, and a third calender rollwhich defines a second nip with the second calender roll; a plurality oflift-out rolls, wherein a first lift-out roll is positioned such thatthe web travels over the first lift-out roll as it extends between thefirst nip and the second nip; and a first closing member extendingbetween the second calender roll and the first lift-out roll, theclosing member supporting the web as it travels from the first nip tothe second nip, the closing member not extending through the first nipor the second nip, the closing member being a belt, wire, or metal wirewhich travels over the first lift-out roll and at least one additionalguide roll, wherein the first closing member picks the web up from thesurface of the second calender roll, and a second closing membertransfers the web from the first closing member onto the surface of thethird calender roll.
 14. A calender in a paper machine, for thetreatment of a web traveling therethrough, the calender comprising: aplurality of calender rolls in a roll stack defining a plurality ofnips, the roll stack having a first calender roll which defines a firstnip with a subsequent second calender roll, and a third calender rollwhich defines a second nip with the second calender roll; a plurality oflift-out rolls spaced from the calender rolls, wherein a first lift-outroll is positioned such that the web travels over the first lift-outroll as it extends between the first nip and the second nip; at leastone first belt which extends about the first lift-out roll and travelsin an endless cycle, the first belt supporting the web as it travelsfrom the first nip to the first lift-out roll, the first belt notextending through the first nip or the second nip; and a first guideroll located within the endless cycle of the first belt which pressesthe first belt against the second calender roll, the web travelling fromthe first nip to the second nip.
 15. The calender of claim 14 furthercomprising: a second guide roll located within the endless cycle of thefirst belt which presses the first belt against the second calender rolldownstream of the first guide roll; and a third guide roll locatedwithin the endless cycle of the first belt, the web not traveling overthe third guide roll.
 16. A calender in a paper machine, for thetreatment of a web traveling therethrough, the calender comprising: aplurality of calender rolls in a roll stack defining a plurality ofnips, the roll stack having a first calender roll which defines a firstnip with a subsequent second calender roll, and a third calender rollwhich defines a second nip with the second calender roll; a plurality oflift-out rolls, wherein a first lift-out roll is positioned such thatthe web travels over the first lift-out roll as it extends between thefirst nip and the second nip; at least one first belt which extendsabout the first lift-out roll and travels in an endless cycle, the firstbelt supporting the web as it travels from the first nip to the firstlift-out roll, the first belt not extending through the first nip or thesecond nip; and a first guide roll located within the endless cycle ofthe first belt which presses the first belt against the second calenderroll, the web travelling from the first nip to the second nip; a secondbelt traveling in an endless cycle and extending around a secondlift-out roll; and a second guide roll located within the endless cycleof the second belt which presses the second belt against the thirdcalender roll, the web traveling from the first belt to the second beltas it travels from the first nip to the second nip.